Metallic filaments and method of making same



l R. B. POND March, 4, 1958 METALLIC FILAMENTS AND METHOD QF MAKING SAME 3 Sheets-Sheet 1 Filed Oct. 20, 1953 INVENTOR Roar/PT a. FDA/0; KM R Q ATTORNEY March 4, 1958 R. B.'POND 2,825,108

METALLIC FILAMENTS AND METHOD OF MAKING SAME Filed on. 20, 1953 s Shets-Sheet 3 7 SWNKmE MIR/65 INVENTOR ATTORNEY United States Patent METALLIC FIL AMENTS AND METHOD OF MAKING SAME Robert B. Pond, Westminster,-Md., assignor to Marvaland, Inc., Baltimore,=Md., a corporation of'Maryland Application October 20, 1953, Serial No. 387,137

Claims. (Cl. 22-4001) This application relates generally to improvements in the. art of metallurgy and has particular reference to a cast metallic element and the method and apparatus for making the same. This is a continuation-in-part of my application Serial No. 220,588'filed April 12, '1951, now abandoned. I

More specifically, the invention deals with the transformation of molten metal into a solid product in the nature of a filament. Such a product, as produced'by the method and apparatus hereinafter disclosed, maybe used in almost every instance where similar products made-by other methods are employed and, due 'to the simplicity of themethod and appara-tus'utilized to produce theprodnot, it is capableof being made very economically and at the point of usage. Among various-commercial uses of the product-are-included those of thermal insulation, radio shielding, electrical resistors, special applications such'as in-chemicalprecipitation or chemical reaction tanks, ornamental tinsels; =and, in military use, it providesan effective means for jamming radar reception in ,both otfensive and defensive warfare.

:Metal filaments-may be divided, broadly, into two classes, the rod or wire type and the ribbon'type. In both instances, the ratio of the length tothethickness of the element-may be extremelylarge, and in the case o'fa ribbon filament the ratio of the length'to the Width may be also extremely "large Where the ratio between width and-thickness is relatively great. Heretofore,'inthe production of wire'type filaments, it has been the practicefto draw metal wires into small'diameters, and ribbon-type filaments have been produced byJfleit-rdlling'filament'wires Z,8Z5,l08 Patented Mar. 4, i958 tration, isshown in "the accompanying' drawing; but-it is tobe'expressly understood'thatsaid drawing is employed merely "to facilitate the description'o'f-theiinvention as*a whole and-not to' define the limits thereof, "re'ferencebein'g had-to the appended claims for thi's purpose.

Inth'e drawings:

Fig. 1 is a top plan view of an apparatus capableof carrying out thepurposes of the invention;

FigJZis anenlarg'ed'longitudinal section thereof "taken substantially 'on the line -22 of'Fig. 1;

Fig. 3 isa graph showing variation'of filament thickness and length with impingement velocity; n

Fig. '4'is 'a graph showing variation of filamentjthickness and len'g'th'withejection velocity;

'FigKSis a greatly'enlarged top plan-view ofa'pieceof filament, and I Fig. '6is"a greatly enlarged bottom" plan'view of the same piece offilament. I

The app'aratu'st for making the product of the present invention a d'forca'rrying'out the process'herein'disc'losed prefeirediform, of 'a'base 3 upon whichis illing jagent in the form of a rotary open mold "chill block"4;ma'de ofLa material having high con 'ductivity fan'd .fstre'ngth, whose melting temperature is above-that bf tn fme'ta'l from which the filament 'i's formed, "and wlii'ch possesses sufficient mass to :dissipate not only thesupe'i'heafinduced 'byLr'aising theternperature or by slitting metallic foils by various 'methods.' These practices arekn'ownto'produc'e plastic deformation ofthe metal so that, in its newly formed 's'tate,'cons'iderable residual stress, as well as a greatly distorted grain form; exists inth filament. I

In accordance with the present invention, his proposed toproduce a 'rnetallic'element wherein'no'plastic deformation is involved, with the consequence that no .jgreat 'residualstress existsin said element nor isthere any'distortionin the-grain form of the metal. This d'esider'aturn is accomplished'by casting the element directly from'a molten material.

Extensively conducted experiments have shown that all non-refractory metals or alloys suchas'tin, 'lead, cadmium, indium, zinc, bismuth, aluminum, magnesium, copper and their alloys, and other metals and alloys of the general class specified, can be employedin making the product herein described.

It vis further contemplatedthatthe three-dimensional measurements of theelementsproduced may be controlled unity so'th'at thefilam'ent becomes a particle of flake powder. Therefore, it is to be understood'that'the term filament as used inthe 'following'specification :and claims. is

intended to tinclud'e an element of powderform.

The' inventivew idea involved, is 1 capable of receiving I a varietyof expressions one of which,for purposesof illusof the metalaboveits melting pointfbut *alsofthe latent heatof'fusi'on o'f the'filame'nt as 'it isformed j'onthe surface of the'bl'ock from tlie stream of molten metal pinging thereon. The block is of jniate'rial of "great strength .becauseof thehi'gh s'p'eedsat'which the samejis rotated.

Although the chill block 4 has beenishown as having considerable mass, which .is the desirable form .of constructing the same experiment'shave indicated that the open moldmay takethe form of a cylinder or cone also of considerable mass, or may be a continuous metallic belt upon which themolten metal impinges. Each of thesefl'atter types of moldhasproven togive limited service in the production of filaments from certain oft'he metals hereinbefore mentioned including .those having high' liquid surface tension,- as hereinafter referred to. Howevenit has been found thatwhen'the'chilling agent doesnot possess sufiicient mass to dissipate theiheat of fusion of the metal being impinged upon it, there can be provided antexternal coolant forsaid agent, and thistmay be accomplishedin ,any' desired and well known manner.

TIhe-chillTblock 4, as shown,.must be provided with avery'smooth, polished open chill :su'rface preferably in .theform ofa vspherical or ellipsoidal concavity 5. .The exact -curvature=of this surface will vary :as the surface tension .ofthe metal used to produce thefilarnents. .By having a concave surface, the centrifugalaction of the mold developsin the-molten metal a higher. normal force against the mold surface, thereby rupturing the surface of the metal. at thepoint ofimpact and producing the intimate contact desired andiits accompanying chilling effect. lThus, use is made of'the-centri'fugal forcein the metal after-impingement tobreak down the-surface tension and: facilitate freezing. Thelhigher the surface tenw sionotthe gfilament material. at the temperatureof ejection; thereof' toward the J mold, the more difiicult it is toforcethe stream against themoldwith sufficient velocity-to cause-that-surface or intimate contact-which facilitates heat flow from the liquid stream tothe chill block,-and the shorter need be theradius oftheconcavity 5 in order to accomplish the desired chilling eifect;,- and thus it is contemplated that-thecurvature 'of the mold .surfaceimaybechanged tomeet varying conditions. fllhis type of surface has the advantage of varying-surface velocityas theimpingementypoint is varied, inYa manner ne ates to presently appear, from the center to the outer periphery of the surface.

The chill block 4 is driven about its vertical axis of rotation by means of a high speed motor 6 suitably mounted on the base 3. It is desirable that the speed of the motor may be varied to cover a rather wide range as it has been found that speeds of from approximately ten to thirty thousand R. P. M. have produced efficient results. In any event, it is essential that the surface speed ofthe chill block at the point of impingementv of the molten metal be sufficiently high to cause the metal, solidified by contact with the surface as a result of removal of the latent heat of fusion from the liquid, to be rapidly cast off by centrifugal force generated by the rotating block.

It has been stated that the chill block 4 should be provided with a very smooth polished surface 5. The smoothness should be such that there are no reentrant or sharp angles or surface changes more than those of the thickness within the width of the filament being produced.

Finishes have been effected on the chill block of from less than 1 microinch to approximately .001 inch, as checked with a profilometer. A coarse finish can only be used on heavy filaments and even then it has been found difficult to have the equipment operate well in a continuous manner. Thin filaments have been produced on a surface finish of from less than 1 microinch to approximately 40 microinches. Roughly speaking, the surface finish cannot be coarser than the thickness of the filament to be produced.

A continuous flow of molten metal to the surface 5 may be accomplished in various ways and, as shown herein, this result is attained by employing an openended container or ejector tube 7 provided at one end with a nozzle 8 having a restricted orifice 9 whose size may be regulated in any suitable manner such as by removably mounting said nozzle so that it can be replaced by another one having an orifice of different dimension. The opposite end of the container formed by the apertured head 10 is designed to receive, through its inlet, pressure which may be mechanically or pneumatically generated. For this purpose, said head 10 has connected thereto a pressure inlet pipe 11 adapted for connection to any suitable source of pressure supply (not shown) capable of varying said pressure to eject the molten metal through the orifice .9 in a stream and onto the revolving surface 5 with a velocity that will force said metal to make such intimate contact with said surface that heat will flow from said metal to thus produce solidification thereof. The molten metal, the temperature of which may be varied in accordance with the particular metal used and which may be increased above the melting point of the metal in order to increase its fluidity, is supplied to the container 7 from a reservoir 12 mounted thereon and from which the flow into the container may be regulated by a valve 13 in the outlet of the reservoir.

The container 7, whose nozzle 9 is disposed in proximity to the surface 5 so that the point of impingement will coincide with a radius of said surface, is carried at an incline by a wide support 14 on the base 3, and a dovetail connection 15 between said support and container enables the latter to be slidingly adjusted to vary said point of impingement of the molten metal along a line coincident with said radius or, in other words, to different positions between the center of rotationof the block 4 and the periphery of its surface. The purpose of providing this variable will become apparent as the description proceeds. It will be understood, of course, that the materials of which the container 7, its nozzle, the reservoir 12 and associated parts are made, must necessarily be such that they will not readily alloy with the molten metals since this would result in deterioration of the apparatus.

It is now apparent that the metal is ejected from the container 7 as a liquid stream and impinges on the open surface 5 of the chill block 4 as a liquid, and that the superheat and the latent heat of fusion is removed from the liquid by intimate contact with said block, and is thus solidified and thrown from the surface 5 by the centrifugal force produced by rotation of the block. Therefore, continuity exists between the molten metal in the container 7, the molten metal in the air on its course to the surface 5, and the liquid and solid metal on said surface; and also between the solid metal onsaid block and that which has already left the block provided, of course, that the variables hereinafter described are controlled so as to produce a continuous filament which latter effect can be produced by a constant maintenance of supply of molten metal in the container 7.

The variables (1) temperature of the molten metal, (2) velocity of ejection from the container 7, and (3) the size of the orifice 9 can be correlated with (4) the surface speed produced by the rotating block 4 at the point of impingement of the molten metal to cast filaments of various thicknesses, widths and lengths; and, by altering one or more of said variables during the cast ing process, actual variations in said dimensions may be accomplished.

Generally speaking, it can be stated that the higher the temperature of the molten metal and the slower the ejection velocity thereof, with a given orifice size and mold surface speed, the thinner the filaments. Also, with all other variables held constant, the closer the velocity of ejection approaches that of surface speed at the point of impingement, the greater the continuity of the produced filament. Further, with all other variables held constant, the larger the orifice size, the wider the filament.

The formulae for these controls may be more specifically explained as follows. If the surface speed of the chill block at the point of impingement is fixed, and the impingement point is held at some constant distance from the center of rotation with the orifice size fixed, the length as well as the width of the filament or filaments is fixed. However, there are still available two other variables, namely, the temperature of the molten metal and its ejection velocity. If it be assumed that the temperature is held constant and the ejection velocity is varied, an increase in the latter will effect a tendency on the part of the molten metal to pile up on the chill block with the result that the filament will increase in thickness. Conversely, as said ejection velocity is decreased, said pile-up is lessened until, at a given velocity, the thinnest continuous filament possible will be produced with the .given working temperature of the molten metal; and further reduction in said velocity will result in discontinuous filaments. Progressive reduction in the ejection velocity will produce shorter and shorter filaments until,

as previously suggested, the length to width ratio of the filament approaches unity and the filament becomes a particle of flake powder.

In the event that a variation in the thickness of the filament is desired without altering the ejection velocity, the method of control can be found in the temperature of the molten metal. If this temperature is increased, the fluidity of the metal is increased or, in other words, the surface tension of the metal is decreased and a greater energy is imparted to the metal. This excess energy must be absorbed before the metal solidifies or, otherwise, during the period of contact with the chill block the metal will be in a liquid form for a longer period of time. If the ejection speed is such as to pro duce discontinuous filaments at one temperature, then at a higher temperature the filament will become continuous although the amount of metal ejected per unit of time is the same, and a thinner filament will be the result. Thus, in'order to produce the thinnest filament possible, an exceedingly high molten metal temperature is used with some minimum ejection velocity relative to same -exeeedingl hign sur'tate speed at the-paint dean piiigem'eht."

Assumingnow thatthe temperature; speed ef 'ejeetieh; orifice-size, and *p'eddfiibteitidhof "the chill block are all"maintained"constangit is pos'sible' -under th'ese condi tibns to" alter "theieifective"siirface' spec at the "point 'of impingement by "translating' this" point between "a position slightly" offset from the 1 a'iiial center er" the bloclc and a position adjacent the peripheral edge thereof. "It' may be assiirnedithat, withthe-above constants, 'the"'thinnest continuou's' filament is produced "witlrthe impingement point located halfway between said-limits; Underthis assumption, adjustment Of the container 7 with its nozzle 8, in the manner heretofore described, toward .the center of rotation er" the block "4 will "continueto produce an endless filarne'nt biitit willbeco'rrle progressively thicker and, conversely, translation of the ne'zzle teward the periphery of the 'blo'ckwill produce discontinuous filaments of decreasing lengthsuntiltlie "ab-eve "mentioned powder material is attained: arena-um also be noted that a long continuous filament -can be .produced which'has a varying thickness; by moving the point of impingement-slowly toward the'center ofr the moldsurfacewhile said filament is being formed. If *the angle-of incidence which ,the stream of molten metal forms with the-surface of the chill block isvarie d; no apparent.effeetppomthe filament isfobserved How ever, the angle of incidence with -which the -solid meta'l leaves the surface is a function of the continuity o'frfilament, the-thickness and width, thereof or mass per innit length, the density of the metal -used,; the degree of polish of the surface 5 and the surface speed of the chill Block "at the "point of impingement; This, "the"aii'ig'le"' of incid'n'ce' 'of the departing'solid metal can e fixed' lltitiV'e to "some external "instrumentality 1151i '23. 'bb'l lecting bin or the'like since the'poin't (if departure is dependentupon the point at which "the filfolth A fiifa'l ifi'i pingesLrelative/to said: instrumenta'lity. Hence,"with the trajectory {of-'' the filament fixed, it-. is possible to: aim the departing filament-in aigivenjdirec'tion'. n v

Big. 3 is a graph showing the variation of length and thickness with the parameter of impingement velocities. Fig. 4 is a similar graph showing the variation of length and thickness with the parameter of ejection velocities.

With respect to Fig. 3, as the ejection velocity is maintained at about 150 feet per second (orifice size, temperature of metal and type of metal or alloy being constant), there will be continuous filaments (ranging in thickness from 1000 microns down to just above zero) as the impingement velocity is increased from, say to 400 feet per second. Thereafter, there will be discontinuous filaments with a progressive decrease in length untilaa.flake powder stage, is. reached. wellbefore -an impingement velocity of 1000 feet per second is reachedl.

As seen in Fig. 4, with an impingement velocity maintained' at"600"feet'persecond (and with" orifice size,- temperaturenf metal and typeof metal or' a-lloybeing constant) there will be "a flake powder'withejection've= 0nd? 'Discontinuous filaments"will'be"'evident'before"300 and these :increase in length until; i when the ejection ve-' locit'y reaches about 600 feet :per seeond,' continuous: fila ments result.

The minimum thickness figure indicated. by.- thedark lines'inFigs. 3 aria 4 is 1.0 micron. These grap'h spFi'gs. 3 and 4, show tendency curves. It will be appreciated that the shape of the curves and their positions relative: to the abscissa and ordinate will vary as the metal oralloy is varied,.,or as. theorifice size, or temperature of the specific metal changes, or as .the relative ejection and impingementvelocities -change.- .-'1 "he figures do,. --howfever; illustrate theextent o'f contro'lpossible. The pi-e cis'io'n'of control is; ofcourse",no "be'tter thanthe pi"e-- clsi'cnetcontrolpf'alr the'v'ariab'les'."

' B-y using- ,"-chill=-'block such as described with surface impingemen speeds varying from slightly above zero to one thousand feet per second, filaments have been produced whose minimumdimensions range from approximately ls8 -to 4.0-' microns in width and thickness, and aslong a's 'two thousan'd *feet. Under ideal conditions filaments-havin a rninirnum thickness 0f 1 micron "and a minimum width of 1 micron can be produced.

F Itf'shoiild be fiirther notedthat with' the production of a giv'e'n thickness of filament, the heat which must be abs'o'rbed by the chillblock per unit-of time increases asthe width-6f the" filament increases sothat with unii'sually wide filaments itfis -riecessary to provide an external 'c'eolant ter the chill block, or otherwise the length or the filament produced --during any one run of metal is limited.

In actual experiments, "the greatest thickness and width so-"farprodhced in a continuous filament are a niicrens thicknessand a SOOO-microns width. The greates't thickness ahd width so far prod'uced'in discontinuous filaments are "a -700-microns' thickness and a 6000-microns wrat -Itshouldhete be noted that thediscontinuity'of the' filament i's "not due to the difference in ejection and impingement velocities but rather 'tothe limited heat capacity'j'of'jthechill block.

Although these minimum and maximummeasurement's may be considered as range's'ffor all practical purposes, it'is 'ndt th beunderstood that the invention is, inany sense, to be limited tosuch-ranges; I Actually, it should be possible, with a continuing supply of molten metal, to extendthe length of a filament to infinity. 7

"As previously ointed out, the type of im ingement surfaceherein-illustratedhasthe advantage of varying surface velocity as-the impingement point-is varied from the center of,rotation to the periphery of the-surface. :This would also-fbe true of the surface of a cone, for as the point--ofimpingementis translated parallel to the axis :of symmetry of the cone the surface-=velocity is changed. However, since the cone has a convex surface, the onlymethod of handling the changing surface ten- --sion p'roblemis by altering the temperature ofthe molten charge;

Mention has been made herein of the .fact that' the filaments produced in accordance with this invention are cast metal filaments. It should now be apparentalso'that these cast metal filaments are solidified in arectilinear shape with only one mold wall, namely, "the smooth polished open surface of the chill b'lock. Actually, the top and bottom surfaces of the cast"metalfribbonetype filaments formed are separately andclearlynidentifiable, only the bottom surface bearing any indications of having engaged a mold surface. Greatly enlarged views of the top and bottom surfaces of such a filament -a'reshown respectively in Figs. 5 and 6.

With regard to Fig. 5 it may be helpful in understand ing this figure if reference is made to a technical paper, TR 3159: E, Journal of Metals, December 1951, Transact'ions AIME. Itis clear from the twofigures however that the upper surface is characterized by shrinkage marks, relief dendrites, andline striae or mammifdrrns, whereas the, bottom surface (Fig. 6) which has engaged the chill block is: smooth with the exception of polishing pit marks, b'uflin'g marks, and the-imprint caused byany engraving or the like on the block;

A cast metal filament may be readily distinguished from filaments formed by other processes, as, for example, a cold wrought or cold wrought and annealed filament, by virtue of ditferences existing inthe microstruc tural characteristicsof the filaments. A cast filament has 7 filament is mosiac compared with the polygonized subgrain structure of wrought and annealed filaments. In accordance with the invention cast metal filaments have been produced where the solidification has been cfof 13", a weight of .6 lb. and a radius of curvature of and having a surface finish of 30 microinches; and employing a glass round orifice having a diameter of 30 molten tin having a surface tension of 526 dynes per cm.

fected at rates of from5O to 1000 feet per second. As 5 at ATs=50, was ejected at 75 ft./sec. at a pressure of 6 will be appreciated from the foregoing description these lbs. The velocity of impingement was 300 ft./sec. and rates may be controllably varied to effect various desired the angle of impingement was 90. Filaments were proresults. duced having a length of 15 feet, a thickness of 10 and In view of the great speed of solidification effected it a width of 200 is pertinent to note the method of measuring the solidifi- 10 Note.The symbol ATs=50 signifies that the temcation rate. The cast filaments formed carry on their peraiure of the metal at ejection was the melting temperabottom surfaces the impression of any mark placed on ture plus 50'. ,u signifies microns. the chill surface. Since the surface tension of all molten metals is high it is obvious that the metal must have v {EXAMPLE solidified while on the chill surface. The metal is never With the same ch11l blOCk, l i 4 flifital as on the chill surface for one complete revolution of the Example ut employing a velocity of e ection of 300 surface (for if it was it would result in overlay or piling at a Pressure of 151138 and an angle 0f p up of the material). In fact, with the present invention ment f f, fila w e p u having a length of as described, only about one-half inch of the filament 22 feehathlckness 0f 27la11daW1dth Of 1* contacts the surface at any one time, that is to say, the EXAMPLE 3 molten metal goes onto the surface of the chill block at i the same rate that the solid cast metal comes off. Then, 111 3115 example, @1111! block Example 1 since it is transformed from a liquid to a solid while on e p y t ith a fin1sh of 2 micromches. The the rotating chill block, its minimum velocity ofsolidifiorlfice e was of slhcon carblde- Tm having a cation can be calculated knowing the speed of the surface fifce tenslon of dimes P at ATS=200 was at the point f impingement and the length f fil t e ected at a velocity of 75 ft./sec. at a pressure of 6 lbs. making Contact at any one time The velocity of impingement was 300 ft./sec. and the an- So that the invention willlbe more clearly understood, is lmpmgement was Elements were p p h f ll i ifi examples are given; having a length of 75 feet, a thickness of 6.5 and a width 30 of 220g. EXAMPLE 1 These and other examples of tin are listed in the Employing an aluminum chill block having a diameter following tabulations:

Chill Block Orifice Metal Election Impingement Filament;

D. Wt. 0R. F. M. Sh. D. ATs s. T. V. P Vi. A. T. w. L.

Al 3" .6# 5 30 Glass 0 30p 52s '15 IL/sec o IiOOitJscc. 00 10 200 15ft. Al 3" .6# 5 30 Glass 0 50 626 300it.lsec. 15 300 ft./sec. 10 27;; 300;: 22 ft. Al 3" .6# 5 2 sic 0 200 514 75ltlsec. s 300it./see. 6.6;; 220 75tt. Steel 7" 2.41: 10 50 Steel 0 200 514 300ft/sec. 15 300ft./sec. 10 8,. 230p 1001t. Steel 7" 2.4:; 10 50 Steel 0 anon 50 520 75ft./sec. 4 300it./sec. 30 18p 2,0001 10 ft.

Legend: M.Mai:erial. D.-Diame.ter. Wt.-Weight. CR.-Radius of curvature in inches. F.Finish in micro-inches. Sh.-Shaperound. ATs-Sea note above. S. 'I.--Surface tension in dynes/cm. Vr-An approximation of election velocity. P.-Pressure in pounds. VL-Impingement velocity. .L-Angle. T.-Thickness. W.Wldth. L.Length Examples employing zinc as the filament metal are as follows:

Chill Block Orifice Metal Election Impingement Filament M. D. Wt. CR. F. M. sh. D. A'Is 8.1. V. P. V1. A. T. w. L.

Al 3" .6# 5 2 Glass 0 so '100 77s 75ft./sec. 300ft.lsec 30 15,. soo 2. 1.1 a" .6# 5 2 SiO 0 so 100 77s 75l't./sec. s SGML/sec 30 15;: 18014 4111. Al 3" .6# 5 2 Mo. 0 30h 100 I 778 75tt./sec. sooth/see 30 15,. so

Examples employing lead as a filament metal are as follows:

Chill Block Orifice Metal Ejection impingement Filament M. D. Wt. CR. F.. p M. Sh. D. ATS 5.1. V. P. Vi. A. T. w. L.

Steel 7" 2.45% 10 50 Steel 0 an 100 43s 140ft. sec. 9 200 ft. 30 9 480 it.

A1 a" .6# 5 2 Steel 0 so: 43s ftisec. 9 30 4: 590: 1000:; Steel 7" 2.4# 10 50 Steel o 14 100 43s 140ft./sec. a 200tt./sec 30 i p 100it.

enemas employing-"m brass a's'the' filament-metal are:

' hew 'artic le of manufacturecompri'sing a cast I 7 Chill Block Orifice Metal Ejection Impingement Filament M. D. we on; D.' "n'r's s'r. v. i=1 Vi. A. 'r. w. L.

Bass" 4"" 1."a# 5- S10 30,. s0 ;25;n. sge.,,j;;3 l, 000 ft./se c 30 a 0 ,8 Brass 4" 1.3# 5 2 S 0 30p. 50 75 tt./sec. 12 1,000 ftJsec 30 3;; 48p, 75 ft. Brass 4" 1. at 5 SiO 0 30,. 50 150 ft./sec. 1, 000 ft./sec 3,. 180,. 100 ft.

Examples employing copper as the filament metal are:

Chill Block Orifice Metal Ejection Impingement Filament M. D. Wt. OR. F. M. Sh. 1). ATs s1. v. P. Vi. A. 'r. W. L.

Steel 7" 2. 4# 10 50 SiC 0 an 50 100 ft./sec. 60 400 itJsec. 30 9,. 13,. 0,. Steel 10 50 S10 0 so 50 100 ft./sec. 30 400 it./sec. 30 19,. 70,. 1a a. Steel 10 e0 SiO 0 300,. 50 100ft./sec. 3 50it./sec. 30 100.. 1,200,. 100n.

The invention has also been used to make filaments of 25 cadmium, bismuth, indium, magnesium, aluminum and various alloys of these. Among the alloys tried have been Pb-Sn 32-68, 50-50, 60-40; Zn-Sn 50-50; Cu-Zn 70-30, 90-10; Al-Si 97-3; Al-Cu 97-3. (The numbers after the metals indicate the percentages in order.) 30

An example of the effect of a change in the radius of curvature of the chill block is of interest.

An aluminum chill block having a radius of curvature of 10" was used. A round orifice of a diameter of .010" was employed with an ejection velocity of75 F. P. S. 35 and an impingement velocity of 200 F. P. S. Employing tin having a surface tension of 522 dynes per cm. at ATs=100, filaments were formed. But, employing zinc having a surface tension of 778 dynes per cm. at ATs=l00, no filaments would form. However, with everything else held constant, the radius of curvature of the chill block was changed to 5 inches and both tin and zinc then formed filaments.

.It should be noted that aluminum cannot be formed into a filament on a chill block having a 10" radius of curvature regardless of the ATs. Moreover, if no concavity at all is used, and the ejection velocity is kept low, no filament will be produced but instead, the metal will roll off the edge of the chill block in the form of little balls.

In accordance with the invention it is possible to produce a plurality of filaments simultaneously and with the same apparatus. To effect this a plurality of spaced nozzles or spaced orifices may be employed. Other variations of the invention will occur to those skilled in the art who have knowledge of this disclosure.

I claim:

1. A new article of manufacture comprising, a cast metal filament the thickness of which ranges from approximately 1 to 4 microns, and the length of which 30 ranges from approximately 1 micron to infinity.

2. A new article of manufacture comprising, a cast metal filament the width of which ranges from approximately 1 to 4 microns and the length of which ranges from approximately 1 micron to infinity.

3. A new article of manufacture comprising a cast metal filament the thickness and width of which range, from approximately 1 to 4 microns, and the length of which ranges from approximately 1 micron to infinity.

4. A new article of manufacture comprising a cast 70 metal filament having mold marks on one surface only, said filament having a thickness which ranges from 1 to 4 microns, said filament having a relatively great width to thickness ratio and a length which ranges from approximately 1 micron to infinity.

metal filament, said filament having mold marks on one surface only and having non-uniform, comparatively large grains with a microstructure of heterogeneous phase distribution, said filament having a width which ranges from approximately 1 to 4 microns, said filament having a relatively great width to thickness ratio and a length which ranges from approximately 1 micron to infinity.

6. A method of casting solid metal filaments from molten metal which comprises impinging a stream of molten metal against a smooth polished concave open chill surface, rotating said surface, the solidification of the metal being effected at a rate ranging from approximately 50 to 1000 feet per second.

7. A method of casting solid metal filaments from molten metal which comprises impinging a stream of molten metal against a smooth polished open rotatable chill surface in which the plane of the surface forms an acute angle with the axis of rotation of the surface on that side of the surface on which the metal is impinged, rotating said surface, the solidification of the metal being effected at a rate ranging from approximately 50 to 1000 feet per second.

8. A method of casting solid metal filaments from molten metal which comprises impinging a stream of molten metal. against a smooth polished open rotatable chill surface in which the plane of the surface forms an acute angle with the axis of rotation of the surface on that side of the surface on which the metal is impinged, and rotating said surface whereby a component of the force acquired by the metal is normal to the plane of the surface tending to retain the metal on the surface and solidifying the molten metal while the metal is retained on the surface.

9. The method of casting molten non-refractory metal into continuous strips in widths ranging approximately from 1.8 to 5000 microns and in thickness ranging from 4.0 microns to microns, which comprises impinging a stream of molten metal against a smooth polished open chill surface, rotating said chill surface, controlling the speeds of impingement and of rotation so that the metal remains on the chill surface for a period less than required for one revolution, the temperature of the molten metal, the surface tension of the metal being chosen with respect to said speeds to efiect solidification of the metal while on the chill surface at rates ranging from approximately 50 to 1000 feet per second.

10. The method of casting solid metal filaments from molten metal which comprises impinging a stream of molten metal against a smooth polished open chill surface, rotating said surface, and varying the point of impingement of the stream to positions between the center 1 1 of rotation and the periphery of the surface in order to vary the length and thickness of the filament, the solidification of the metal being effected at rates ranging from approximately 50 to 1000 feet per second.

Re. 12,568 Cowing Nov. 27, 1906 Cole Dec. 1, 1903 12 Strange et al. Dec. 1, 1908 Staples Apr. 11, 1911 Staples June 3, 1913 Nagy Jan. 14, 1919 Elmen Dec. 11, 1928 Kann Nov. 24, 1936 Brennan May 27, 1952 Brennan May 26, 1953 Pawlyk Feb. 15, 1955 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 2,825,108 March 4, 1958 Robert B; Pond It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected belowa In the grant, lines 2 and 12, and in the heading to the printed specification, lines 4 and 5, name of assignee, for 'Marvaland, Inc."

read Marvalaud, Inc. in each occurrences Signed and sealed this 21st day of October 1958,

(SEAL) Attest:

KARL HfmINE ROBERT c. WATSON Attestlng Officer Conmissioner of Patents 

6. A METHOD OF CASTING SOLID METAL FILAMENTS FROM MOLTEN METAL WHICH COMPRISES IMPINGING A STREAM OF MOLTEN METAL AGAINST A SMOOTH POLISHED CONCAVE OPEN METAL BEING EFFECTED AT A RATE RANGING FROM APPROXIMATELY 50 TO 1000 FEET PER SECOND. 